In the field of electronics production, it is well known that possible sources of errors are the electronic circuit boards. Mainly, these errors originate from the application of viscous medium, e.g. solder paste, prior to the mounting of components on the board. Over the years, a number of different techniques have been proposed for detecting errors resulting from solder paste application. Originally, this detection was performed manually. Lately, however, the use of cameras in combination with image processing have become the preferred choice for detecting said errors. An example of this can be found in the International Patent Publication WO 00/42381, which discloses a method and a device for contactless inspection of objects on a substrate.
When errors resulting from the application of solder paste have been detected, and preferably identified, appropriate action must ensue. Traditionally, a board containing errors as a result of the application of solder paste is simply taken out of the process. The removed board can then be discarded or, commonly, cleaned and subsequently reinstated at the beginning of the process. Recently, the results of the solder paste application, i.e. critical parameters thereof, are monitored and errors are identified, and the monitored parameters are fed back so that appropriate measures can be taken. This is common in state-of-the-art screen printing applications.
This feedback can, in the simplest case, be a warning message when a parameter has crossed a certain pre-set limit. The operator can then decide which actions to take. On the other hand, an advanced system could incorporate artificial intelligence to adjust application parameters such as, in the case of screen printing, squeegee pressure, speed and angle, amount of paste on the stencil, cleaning interval, etc. Thus, critical process parameters can be monitored and adjusted so that the application errors can be reduced. However, the specific board containing the detected errors is dealt with in the traditional manner described above, i.e. the faulty board is removed from the entire process.
When using conventional dispensing, i.e. contact dispensing, as opposed to screen printing for the application of solder paste, dispensing heads with integrated measurement capabilities, for measuring the result of the application of solder paste, are known within the art. The measured parameters can be fed back for process control in order to reduce future errors. Since the integrated measurement capabilities can measure the solder paste application of a single dot, e.g. immediately following the dispensing of said dot, process parameters can be altered for the subsequent dispensing of dots on the same board. Thereby, small errors can be detected and process parameters adjusted so that, in the best case, major errors requiring the board to be removed from the process, can be avoided.